Interactions between HMG proteins and the core sequence of DNaseI hypersensitive site 2 in the locus control region (LCR) of the human β-like globin gene cluster

HMG proteins are abundant chromosomal non-histone proteins. It has been suggested that the HMG proteins may play an important role in the structure and function of chromatin. In the present study, the binding of HMG proteins (HMG1/2 and HMG14/17) to the core DNA sequence of DNaseI hypersensitive site 2 (HS2core DNA sequence, -10681--10970 bp) in the locus control region (LCR) of the human b-like globin gene cluster has been examined by using both the in vitro nucleosome reconstitution and the gel mobility shift assays. Here we show that HMG1/2 can bind to the naked HS2core DNA sequence, however, HMG14/17 cannot. Using the in vitro nucleosome reconstitution we demonstrate that HMG14/17 can bind to the HS2core DNA sequence which is assembled into nucleosomes with the core histone octamer transferred from chicken erythrocytes. In contrast, HMG1/2 cannot bind to the nucleosomes reconstituted in vitro with the HS2core DNA sequence. These results indicate that the binding patterns between HMG proteins and the HS2core DNA sequence which exists in different states (the naked DNA or the in vitro reconstituted nucleosomal DNA) are quite different. We speculate that HMG proteins might play a critical role in the regulation of the human β-like globin gene's expression.     

Interactions between HMG proteins and the core sequence of DNaseI hypersensitive site 2 in the locus control region (LCR) of the human β-like globin gene cluster

HMG proteins are abundant chromosomal non-histone proteins. It has been suggested that the HMG proteins may play an important role in the structure and function of chromatin. In the present study, the binding of HMG proteins (HMG1/2 and HMG14/17) to the core DNA sequence of DNaseI hypersensitive site 2 (HS2core DNA sequence, -10681-10970 bp) in the locus control region (LCR) of the human β-like globin gene cluster has been examined by using both thein vitro nucleosome reconstitution and the gel mobility shift assays. Here we show that HMG1/2 can bind to the naked HS2core DNA sequence, however, HMG14/17 cannot. Using thein vitro nucleosome reconstitution we demonstrate that HMG14/17 can bind to the HS2core DNA sequence which is assembled into nucleosomes with the core histone octamer transferred from chicken erythrocytes. In contrast, HMG1/2 cannot bind to the nucleosomes reconstitutedin vitro with the HS2core DNA sequence. These results indicate that the binding patterns between HMG proteins and the HS2core DNA sequence which exists in different states (the naked DNA or thein vitro reconstituted nucleosomal DNA) are quite different. We speculate that HMG proteins might play a critical role in the regulation of the human β-like globin gene’s expression.     

The interaction between the human β-globin locus control region and nuclear matrix

Our previous study showed that hydroxyurea (Hu) could induce HEL cells to express humanβ-globin gene. However the molecular mechanisms by which the expression of β-globin gene is activated and regulated are poorly understood. Here we show that the binding patterns between the core DNA sequences (HS2 core sequence -10681- -10971 bp , HS3 core sequence -14991- -14716 bp and HS4 core sequence -18586- -18306 bp) of DNase I hypersensitive sites in the human β-globin LCR and nuclear matrix proteins isolated from Hu induced and uninduced HEL cells are quite different. Results demonstrated that nuclear matrix proteins might play important roles in regulating the expression of humanβ-like globin genes through their interaction with HSs (HS2,HS3 and HS4 core sequences) in the LCR. Moreover, the results obtained from the in vitro DNA-matrix binding assay showed that the core DNA sequences of DNase I hypersensitive sites (HS2, HS3 and HS4) were unable to bind to the nuclear matrix isolated from uninduced HEL cel